Hundreds of species of phytoplankton, algae, autotrophic bacteria, and other autotrophic species occur naturally in both fresh water and oceans throughout the world. Long known as a potential diet supplement, and for certain species a dietary staple for nutritional needs, algae are now being cultivated for diverse purposes including the production of food for fish, mollusks, animals and humans, the treatment of sewage and waste waters and as nutriceutical ingredients and for the production of enzymes having industrial uses. Genetic modification of algae is also now being done experimentally to yield cultures capable of extremely rapid growth and by this replication of custom materials reproduction.
Traditional means of cultivating algae and similar autotrophic aquatic species has been in shallow ponds or raceways, both indoors and outdoors, covered and uncovered. Coverings provide a means of limiting exposure to strong lighting sources as well as preventing random contamination by competing species. In most cases, however, since the cells of these unicellular or conjoined but undifferentiated cells need to be exposed to photonic energy directly, the limitation of the penetration of light rays to a few centimeters from the normal surface of the liquid has limited the usefulness of water more than a few centimeters in depth.
Yuan-Kun Lee, in his article “Enclosed Bioreactors for the Mass Cultivation of Photosynthetic Microorganisms: The Future Trend,” TIBTECH, July 1986, p. 186-189 reviews a variety of recent mechanisms and designs of apparatus intended to provide light to a larger area than merely that of the surface of the liquid. Much attention has been devoted to attempts to distribute light energy evenly across the interface to the liquid medium which results in expensive schemes of custom lighting instruments or fiber optics and other high capital cost items. The present invention is a low cost means of allowing light penetration to almost any arbitrary depth below the surface. No specific means of regulating the uniformity of the distribution of photonic energy to the photosynthetic species is contemplated except that natural solar radiation is expected to be the primary source of light, supplemented only if and when necessary by artificially generated illumination.